Trapped could hardly be more timely. On 2 March the US supreme court heard oral arguments for Whole Woman’s Health v Hellerstedt, the biggest abortion rights challenge in two decades. In June a decision will be made, impacting the safe and legal right to choose for millions of women.

Trapped, which premiered at Sundance, was directed by lawyer turned film-maker Dawn Porter (Gideon’s Army), and follows the ongoing struggles of abortion clinic workers in Texas, fighting against so-called Trap laws (hence the film’s title) to keep the procedure safe and legal in the US. As the documentary explains in one of its many interstitials, the acronym stands for “targeted regulations of abortion providers”. Since 2010, hundreds of these laws have been passed by conservative state legislatures, particularly in the south.

Over the course of Trapped, Porter makes an irrefutable argument that the new laws, though justified by legislators as an attempt to protect women’s health, are in fact only there to limit access to abortion.

The Whole Woman’s Health v Hellerstedt case centers on two such pieces of law passed in Texas that have – since taking effect – already shuttered more than half the state’s 41 abortion clinics. Amy Hagstrom Miller, founder of Whole Woman’s Health, the lead plaintiff in the case, appears in the film, which tracks the battle up until its day at the supreme court.

Porter’s film is armed with a deluge of troubling data to make her case, but it’s the personal stories she captures that make her argument all the more compelling.

Willie Parker, an OB/GYN who moved his family from Chicago to the south to aid in the fight, gets the most face time among the doctors and directors Porter profiles. A churchgoing man, Parker cites his “traditional upbringing in a black baptist church” for his tireless crusading efforts. “When you have a sense of duty about what you do, it allows you to ignore the naysayers,” he says.

June Ayers, owner and director of Reproductive Health Services in Montgomery, also leaves a lasting impression by lending Trapped its sole moment of levity: while giving a tour of her clinic, she delights in showing off her deluxe sprinkler system, used to water the grass – and ward off protesters.

In a film full of heartbreaking moments, the most devastating comes when a clinic worker is forced to turn away a 13-year-old rape victim, who made a four-hour trip to the facility, due to Trap law complications. As a result, the girl’s been “sentenced to motherhood”.

With Trapped, Porter isn’t trying to convert those opposed to abortion: it’s an unabashedly one-sided documentary that preaches to her choir. No anti-choice activists are profiled; they are only seen protesting vehemently outside clinics (one screams “All black lives matter!” to Parker, who is black, as he exits his car), or speaking out against abortion in churches. It’s the right approach. By keeping her film so narrowly focused, Porter succeeds in illustrating the severe toll political debates can take on the lives of both patients and healthcare professionals.